Medium: Kool

Three new downtown shops epitomize the mutation of shopping into cultural event, none more so than Rem Koolhaas's spectacular new Prada store in SoHo.

Like a forest at its ecological peak, its systems of flora and fauna thriving in dynamic balance, the new Prada outpost on Broadway in SoHo amounts to a climax loft, a complex design representing years of urban evolution. Lofts are the cauldron in which art, fashion, performance, and architecture have been roiling for several decades in a brew that dissolves high-low distinctions among galleries, museums, and shopping. Prada's glittery opening -- there was Mayor Giuliani, wading through the thronging beau monde -- signals the emergence of loft culture as a mainstream social force and a challenge to department stores and boutiques.

In the eighties, restaurateurs brought loft living into the public realm with big, gutsy, roaring rooms that made uptown's hushed French restaurants seem irrelevant. Retail stores followed, conceived with a finesse that made each sale item seem a precious work of art. The idea was to leave big volumes of space intact without obsessing over details. In his eponymous store, Murray Moss adapted the principle of hands-off museum display to housewares. Richard Serra's Torqued Ellipses inspired Kawasaki Takao, Rei Kawakubo, and New York's Studio MORSA design for the Chelsea branch of Comme des Garçons. Restaurant by restaurant, store by store, SoHo and TriBeCa emerged as New York's most visible design laboratory, but nothing turned up the Bunsen burners so much as the triumvirate of stores whose openings converged this fall: MOMA Design Store, the work of 1100 Architect, opened its off-campus outlet on Spring Street; and Frank Gehry, with his son Alejandro and architect Gordon Kipping, did the Issey Miyake shop in TriBeCa. With Prada, they are revealing windows into the current state of design.

At the corner of Spring and Crosby Streets, architects Juergen Riehm and David Piscuskas, of 1100 Architect, wrapped moma's store in a blanket of light: Translucent panels cover banks of fluorescent tubes on the entire west wall and ceiling, and frosted glass angles around columns. Renouncing the first tenet of modernism -- that structure defines buildings -- the architects dematerialized the supporting walls and columns. The usually solid boundaries of the space have taken on the indeterminate spatial character of the computer screen, neither flat nor deep but somewhere in between. By distilling the store to an essence of light and space, the architects elegantly sidestep the dirty little secret of most lofts -- that their big open spaces are usually dull.

In the Issey Miyake showroom, by contrast, Frank Gehry bites the bullet and fills the void with a signature art piece, a complex stream of metallic ribbons flowing near the ceiling. Kipping, who designed the rest of the store, emphasizes the shell by exposing the rough ceiling joists, and he opens the space to basement displays with carpets of fritted glass. Gehry has basically imported one of his curvilinear façades into the space in a gesture that echoes Miyake's folded, pleated fabrics, which collapse structure and surface into the same material. This interior may not be Gehry's most convincing work, because breaks in the ribbon subvert the illusion of movement. But the sculptural piece addresses the classic loft problem of emptiness by stepping into the vacuum with an object.

At Prada, Rem Koolhaas, architecture's bravura contrarian, fills a similar vacuum -- with a void. Much of Prada's retail space is actually in the basement, and to lead customers there, Koolhaas scoops out the ground floor, creating a stunning wave of space that sweeps down the front and up the back. That magnificent hollow, the store's one spatial gesture, doubles as an amphitheater of stepped seats facing an undulating wall, surfaced in zebra wood, that pivots down to reveal a stage. This space was previously occupied by the museum shop of the downtown Guggenheim, an institution much criticized for commercial creep. Koolhaas reverses the trend of bringing commerce to art by bringing performance to commerce. After hours, shoes normally arrayed on the amphitheater's steps are removed, and the wire-mesh cages riding overhead, displaying dresses, regroup at the back of the store, out of culture's way.

With an assist from the design firm ARO, the Dutch architect pressed into service not only the apparatus of assembly-line factories but also that of libraries: Former bookcases glide on tracks, allowing instantly changeable configurations. Updating the ballet mécanique of movable displays with wireless technology, Koolhaas achieves a flexibility that means the store need never be the same two days straight. With off-the-shelf parts and materials and an electronic pulse, he has engineered a space of flux without resorting to a streamlined visual imagery that implies movement.

Customers join in the interactivity when they step into changing rooms: They can push buttons on an electronic panel to dim lighting and surf Prada's database for items that have escaped the nearby racks. They see themselves on a screen inset in the mirror, for simultaneous real and virtual images. Meanwhile, video feeds stream grainy Italian movies and fashion shows onto wall panels that become magazines of moving images. This is a deeply mediated environment: You're on a screen not far from other screens with movie stars and fashion models, taking part in a cinematic ad world in a state of constant flow and sizzle.

If Gehry as an architect is the Catholic sensualist, cultivating the flesh of architecture, Koolhaas is the Calvinist who, alone among the world's prominent architects, does not bring a signature visual imagery from job to job. He is less interested in elaborating space and form than in invisibles and intangibles such as program and concept. At Prada, though materials like the transparent cellular polycarbonate ceiling, which multiplies and warps the lights it covers, are very carefully chosen, he did not even try to occupy the space with a sexy object. Creating instead an area to be played by the managers and customers themselves, he set up the conditions in which users stir the life in the box.

The interactivity in the changing room, and the sense that the whole promenade down into and up from the hollow is a real-life fashion ramp, adds a dimension of experience to shopping. Koolhaas is really operating on the architecture of shopping, charging the space with a sense of energy. Because he forgoes the more obvious subjects of architecture, Koolhaas is often accused of being a facile, even cynical designer, but here he has pulled an unexpected amalgam out of the hat, putting together many knowns into a new, very fashionable whole.